On 2022-07-21 15:06:45 [+0200], Mike Galbraith wrote:
> That's in tip, but pulling my bandaid off...
>
> [ 3.903338] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
> [ 3.903340] in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 389, name: systemd-udevd
> [ 3.903340] preempt_count: 0, expected: 0
> [ 3.903341] RCU nest depth: 1, expected: 1
> [ 3.903342] CPU: 0 PID: 389 Comm: systemd-udevd Tainted: G E 5.19.0.g96ff3a1-tip-rt #8 3a0ec7519629dbce1c881d809a8600cfad8358ca
> [ 3.903344] Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C 09/23/2013
> [ 3.903345] Call Trace:
> [ 3.903346] <TASK>
> [ 3.903347] dump_stack_lvl+0x44/0x5c
> [ 3.903352] ? migrate_disable+0x37/0xa0
> [ 3.903354] __might_resched+0x171/0x1c0
> [ 3.903357] rt_spin_lock+0x2d/0x70
> [ 3.903361] crng_make_state+0x80/0x1d0
> [ 3.903364] _get_random_bytes.part.15+0x4e/0x120
> [ 3.903366] ? nvkm_vmm_iter.constprop.11+0x311/0x860 [nouveau 9c7d46b64ad6b15f254390d4ef3bd03268a3030d]
> [ 3.903449] ? nvkm_vmm_sparse_unref_ptes+0x80/0x80 [nouveau 9c7d46b64ad6b15f254390d4ef3bd03268a3030d]
> [ 3.903518] ? gf100_vmm_pgt_sgl+0x230/0x230 [nouveau 9c7d46b64ad6b15f254390d4ef3bd03268a3030d]
> [ 3.903588] default_pointer+0x2a0/0x2d0
> [ 3.903591] vsnprintf+0x35e/0x4c0
> [ 3.903593] ? gf100_gr_object_new+0x2b/0x70 [nouveau 9c7d46b64ad6b15f254390d4ef3bd03268a3030d]
> [ 3.903669] va_format.isra.16+0x6e/0xa0
> [ 3.903670] vsnprintf+0x35e/0x4c0
> [ 3.903673] vprintk_store+0x140/0x540
I remember asking why it is needed to disable interrupts across
vsnprintf(). John, can I take this as-it or are you sending a new batch?
> Bandaid:
>
> printk: fix RT vprintk_store() might sleep splat
>
> RT can't call vsnprintf() with IRQs disabled, so disable migration
> and move the printk_enter_irqsave() call down to where it's needed.
>
> Signed-off-by: Mike Galbraith <efault@xxxxxx>
> ---
> kernel/printk/printk.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2277,8 +2277,7 @@ int vprintk_store(int facility, int leve
> int ret = 0;
> u64 ts_nsec;
>
> - if (!printk_enter_irqsave(recursion_ptr, irqflags))
> - return 0;
> + migrate_disable();
>
> /*
> * Since the duration of printk() can vary depending on the message
> @@ -2313,6 +2312,11 @@ int vprintk_store(int facility, int leve
> if (dev_info)
> flags |= LOG_NEWLINE;
>
> + if (!printk_enter_irqsave(recursion_ptr, irqflags)) {
> + migrate_enable();
> + return 0;
> + }
> +
> if (flags & LOG_CONT) {
> prb_rec_init_wr(&r, reserve_size);
> if (prb_reserve_in_last(&e, prb, &r, caller_id, LOG_LINE_MAX)) {
> @@ -2369,6 +2373,7 @@ int vprintk_store(int facility, int leve
> ret = text_len + trunc_msg_len;
> out:
> printk_exit_irqrestore(recursion_ptr, irqflags);
> + migrate_enable();
> return ret;
> }
>
Sebastian
